... the GESIPA closed-end blind rivets (and blind rivet nuts) are called "CAP" in the catalogue. They should be used when riveting should be airtight or watertight.
The CAP blind rivet itself is always tight. A quick glance at the rivet is sufficient to understand the reason. However, will the riveting solution be always as tight as the rivet itself?
Closed end rivets are made of a fairly hard aluminium alloy. The hardness of the shaft material however produces only a low hole filling capability. Consequently, hole drilling accuracy becomes a very serious matter indeed. Otherwise, the riveting will not be tight enough to prevent water flowing, not through, but around the set rivet.